Segment Information Net Sales Including Intersegment Sales (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	$ 2,500.4	$ 2,461.3	$ 7,653.4	$ 7,469.8
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	2,519.3	2,476.1	7,705.1	7,515.0
Operating Segments | Passive Safety
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	1,952.4	1,898.7	5,976.0	5,883.5
Operating Segments | Electronics
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	566.9	577.4	1,729.1	1,631.5
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	0.8	1.1	2.7	3.1
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	$ (19.7)	$ (15.9)	$ (54.4)	$ (48.3)